Impact of Calcium and Two Doses of Vitamin D on Bone Metabolism in the Elderly: A Randomized Controlled Trial

Randomized controlled trial in ambulatory overweight adults aged 65 years or older with vitamin D insufficiency (screening 25OHD 10 to 30 ng/ml) recruited from three centers in greater Beirut, Lebanon. A total of 257 participants were randomized and 222 were analyzed after 35 dropouts; allocation was stratified by center and sex.

Both groups received calcium citrate tablets orally for 12 months, 4 tablets/day providing 1000 mg elemental calcium and 500 IU vitamin D3 daily. The low-dose group also received weekly placebo tablets, while the high-dose group received weekly 10,000 IU vitamin D3 tablets, for total vitamin D intakes of about 600 IU/day versus 3,750 IU/day.

Higher-dose vitamin D increased serum 25OHD more than the 600 IU/day regimen, but it did not improve overall skeletal outcomes. At 12 months, 25OHD rose to 36.0 ± 9.7 ng/ml in the high-dose group versus 25.9 ± 6.9 ng/ml in the low-dose group, with a larger percent increase in the high-dose arm (95.5 ± 91.8 vs 44.0 ± 58.22; p < 0.0001). Calcium, creatinine, phosphorus, 1,25(OH)2D, PTH, osteocalcin, and Cross Laps showed no meaningful between-group advantage, and BMD at the total hip, femoral neck, and lumbar spine was not superior with the higher dose. The only skeletal signal was a small between-group difference for subtotal BMD change (p = 0.037), and the authors concluded that there was little added benefit from exceeding 600 IU/day in this population and no increase in adverse effects.

Follow-up was limited to 12 months, so fracture outcomes and longer-term skeletal effects were not assessed. The sample was restricted to ambulatory overweight older adults with vitamin D insufficiency in the Beirut region, which limits generalizability. All participants received calcium plus vitamin D background supplementation, so the trial primarily tested different vitamin D doses rather than vitamin D versus no supplementation.